Tandem bucket paving machine



Dec. 2, 1947.

R. A. BECKWITH TANDEM BUCKET PAVING MACHINE Filed May 11, 1944 9Sheets-Sheet l Dec; 2, 1947. BECKWH'H 2,431,682

TANDEM BUCKET PAVING MACHINE 9 Sheets-Sheet 2 Filed May 11, 1944 Dec.'2, 1947. R. A. BECKWITH 2,431,682

:I'ANDEM BUCKET PAVING MACHINE I Filed May 11; 1944 9 Sheets-Sheet 5-Dec. 2, 1947. R. A. BECKWITH TANDEM BUCKET PAVING MACIINE Filed May 11,1944 9 Sheets-Sheet 4 an) LE Dec. 2, 1.94 7.

R. A. BECKWlTH TANDEM BUCKET PAVING MACHINE Filed May ll, 1944 9Sheets-Sheet 5 Du inn To:

- Dec. 2, 1947.

R. A. BECKWITH TANDEM BUCKET PAVING MACHINE 9 Sheets-Sheet 7 Filed May11, 1944 3 1947. R. A. BECKWITH TANDEM BUCKET PAVING MACHINE Filed May11, 1944 9 Sheets$heet 8 Dec. 2, 1947. V B KWW-H 2,431,682

.TANDI EIM BUCKET PAVING MACHINE Filed May 11, 1944 9Sheets-Sheet 9 'FiaIE I flan/22%; BY

Patented Dec. 2, 1947 UNITED TANDEM BUCKET RQVING MACHINE Raymond A.Beckwith, Milwaukee, Wis., assignor to Koehring Company, Milwaukee,Wis., a corporation Application May 11, 1944, Serial No. 535,137

Claims. 1

This invention pertains to the art or" concrete pavers or distributorsof the type comprising a suitable portable base, a concrete mixingmachine mounted thereon, and a boom and bucket distributor unit, thebucket of which traverses the boom when loaded from the mixer, towardthe outer end of the boom to a dumping position at which the concreteconveyed thereby deposited upon the subgrade to be paved.

Concrete paving machines or the above type are well known in the art,and typical constructions thereof are found in Lichtenberg Patent No.1,141,470, issued June 1, 1915, and Tranaas Patent No. 1,824,580, issuedSeptember 22, 1931.

It is customary in the above class of paving machines for the entirebatch of concrete in the mixing drum, or in one of two mixing drums whenthe machine is of the dual drum type, to be discharged into the conveyorbucket of the boom unit preliminary to the traversing of the bucket outon the boom. Since the cubical capacity of the mixing drums is verylarge, the weight of a batch of material received from the mixing drum,or one of the latter when two are used, by the bucket, is very great.The length of the distributing boom of machines of the prior typereferred to is limited by the capacity of the distributing bucket, theweight of which when filled with concrete has a tendency to overturn themixing machine, especially when the boom is adjusted in a position atright angles to the longitudinal axis of the machine or at an adjustmentintermediate longitudinal alinement and transverse disposition of saidboom. I

The primary object of this invention, therefore, has been to provide aconstruction of paving machine of the general type referred to in whicha double bucket or tandem bucket means are employed in lieu of thesingle distributing bucket heretofore used to travel along the boom ofthe boom and bucket unit. It is possible, by the use of the doublebucket construction of this invention, to split the load of the mixedbatch of materials, thereby substantially doubling the stability of thepaving machine as respects the portable traction base and supportedmixer as compared with'that existing when a single bucket is employedand the boom is adjusted at right angles or nearly right angles to thehighway or longitudinal axis of the machine.

In carrying out my invention, I utilize a generally novel cycle ofoperation of the boom and bucket mechanism. In the first place, Iprovide means to distribute the batch of mixed concrete discharged fromthe mixing drum substantially equally to the two distributing buckets ofthe boom, one of these buckets, the outer one, containing one-half ofthe normal drum batch being caused to traverse outwardly on the boom anddump to any predetermined position similar to practice heretofore used,as typified in the previously identified patents. Upon the dumping ofthis outer or first bucket, the second bucket, also containing aboutone-half of the normal batch mixed in the drum, will be caused totraverse outwardly on the boom until it reaches the outer or firstbucket, at which position the dumping means of the second or innerbucket is tripped and its load is dumped. Thereupon, by the operation ofsuitable novel mechanism the outer bucket is returned to the mixer underpower and is used to push the inner bucket ahead of it at the returntraverse along the boom to the desired position of the buckets at theaxis of the boom where they will again receive the divided mixed chargeof aggregates from the mixing drum.

By reason of the employment of the two boom buckets referred to, it isobvious that only about one-half of the weight of the discharged batchis placed upon the boom in the traverse outwardly thereon of thebuckets, this enabling, of course, the employment of a lighter andlonger boom than has been heretofore utilized and afiording to theimproved stability of the machine, likewise previousl referred to.

Another novel feature of my present invention lies in the design of thedistributing boom of my machine, the same being constructed of an innerstationary and substantially horizontal section at the point of supportof the boom unit, and a pivoted outer section of much greater lengthcapable of being raised and lowered, raised to a relatively high angleto the horizontal, thus permitting of elevating the concrete distributedby the machine to a considerable height far greater than permissible inpresent standard types of machines like my invention, with the resultthat the buckets may discharge their aggregate to elevated places ofdeposit when building walls, elevated hoppers, or like structures.

A preferred embodiment of my invention is illustrated in theaccompanying drawings, in which:

Figure 1 is a side elevation of a tandem bucket paving machine in apreferred form of the invention, dotted lines showing the angle to whichthe outer section of the boom may be elevated for supplying the concreteto elevated structures.

Figure 2 is an enlarged view of the superstructure portion of the pavercarrying certain operating shafts and gearing and the vertical axisshaft for the swinging boom of the boom and bucket unit, many of theillustrated parts broken away because of limitations of space forillustration.

Figure 3 is a view of the tandem buckets and the inner end portion ofthe boom and adjacent parts below those which are illustrated in Figure2, the buckets being shown in, closed condition,

dotted lines indicating the opening limit of the doors thereof andcertain parts broken away because of limits of space.

Figure 4 is a top plan view showing primarily the vane distributor atthe inner end' of the boom, Various clutch instrumentalities forcontrolling the operation of the cable and cable drum means for movementby power outwardly and inwardly of the outer bucket and movement bypower outwardly only of the inner bucket, certain parts being brokenaway adjacent the point of pivotal connection of the boom sections.

Figure 5 is a fragmentary View in elevation looking toward the dischargeend of the mixing drum and illustrating certain of the drive gear ingfeatures of the invention.

Figure 6 is a sectional view taken on Figure 1 illustrating bucket 2| ontrack section '25.

Figure 7 is a fragmentary sectional view taken on Figure 1 illustratingbucket Zion track section 24.

Figure 8 is a fragmentary top plan view showing the inner end portion ofthe boom and certain of the manual operating lever means for controllingthe clutch which energ zes the cable operating devices for the inner andouter buckets.

Figure 9 is a diagrammatic view in top plan illustration of the cableand drum devices for op.- erating the tandem buckets.

Figure 10 is a side view of said cable parts diagrammaticallyillustrated.

Figure lla is a plan view of the indexing or control plate for themanual lever that controls operation of the buckets.

Figure 11 is a side view of the main boom supporting arm or bracketalone, the same supporting the clutch operating lever shaft and sleeve.

Figure 12 is a view of the boom swing bracket alone, same directlysupporting the inner end of the main sectional boom.

Figure 13 is a fragmentary view of the inner end portionof the boomshowing the pivot connection between the sections and showing thesupporting bracket by which the inner section of the boom is connectedto the boom swing. bracket.

Figure 14 is a view in elevation, broken away at the ends, showing thedisposition of the buckets, and operating parts associated therewith,when the buckets are on the straight part of the boom.

Figure 15 is a side view broken away, showing the discharge chute of themixer, buckets, and distributor features, the distributing action of thedistributor being depicted.

Figure 16 is a plan view of certainofthe parts.

4 of Figure 15 also depicting the action of the distributor.

In the accompanying drawings, and describing the specific features ofconstruction of my machine, A denotes a conventional mixing drum havinga ring gear B engaging the spur gear I of a shaft 2 mounted in thesuperstructure framework of the paving machine, said framework carriedby the customary traction base C. The gear I' drives the shaft 2 duringthe operation of the mixing drum A, and on the shaft 2 is a sprocketgear 3 connected by a sprocket chain 40. to a sprocket 4 for drivinggearing in a, gear box 5, to be later further referred to. Also carriedby the shaft 2 is a second sprocket 6 connected by a sprocket chain toto a sprocket on a shaft la disposed in a vertical plane about centrallyof the axis of the drum A and extending outwardly in the direction 'ofthe boom and bucket unit. The shaft 7a is connected by bevel pinions lband lo with a vertical driving shaft 8 supported at its upper end in abearing in an offstanding arm D of'the superstructure frame E of thepaver. This shaft '8 is supported also at its lower portion by means ofa lower offstanding arm F attached to the framework E, and the shaft 8.is constantly driven through the gearing previously mentioned from theshaft 2.

At its lower end and some distance below the bracket F the shaft 8 haskeyed or otherwise fastened thereto a rotative vane distributing wheelor member onto which the batch of mixed materials from the drum A isdirected by the discharge chute G of said drum, the latter being ofusual construction and customarily power driven. The purpose of thedistributor 9 is to spread or distribute about equally between thetandem buckets '2! and 22, later referred to as disposed beneath thisdistributor in the filling of these buckets by the batch of mixedmaterial preparatory to the conveying of the buckets and their contentsto the place of deposit of the m xed materials, by traversing movementalong the boom.

Near its lower end the shaft 8 carries a bevel pinion 8a engaging thepinion 8b of an outwardly extending short driven shaft 80, and saidshaft carries a sprocket gear Ill connected by a sprocket chain Illawith a sprocket H, whereby to transmit the drive of the shaft 8 to theshaft 80 and thence to a countershaft Ila on which sprocket I I iskeyed. The shaft I la carries a bevel pinion I2 which meshes with bevelgears I3 and [4 driving the latter in opposite directions. A clutchhousing I5 is fastened to the gear l3 and by engaging the clutch I511 insaid housing the rotation of the housing by the bevel gear l3 will betransmitted to the drum shaft IE which extends crosswise of the boom,which is generally designated at H, near the inner end of the boom. Thedrum shaft Hi carries cable drums I1 and i8 which, when turnedcounterclockwise by the use of the clutch means l5,and [5a, will movethe front or outer bucket 2i outwardly on the boom H. The previouslymentioned bevel gear M is keyed to a sleeve 19 on the shaft I6, and thissleeve carries at its outer end a clutch housing 28 cooperative with theclutch means 25a therein to drivingly connect under manual control thegear i l with the shaft l6 to'turn the shaft I6 in a clockwisedirection, under which conditions the outer or front bucket 2| will bemoved inwardly on the boom H toward the mixer A. The. drums l1 and I8are, connected. to the, bucket 2! through cable provisions shortly to bedescribed.

Keyed to the sleeve l9 about at the middle relatively to the shaft 16and inside of a cable drum 23 surrounding said shaft and otherwiseloosely turning on the sleeve i9 is a clutch 23a for transmittingturning motion of the sleeve [9 to the drum 23 under suitable manualcontrol of the clutch means 23a. The drum 23 has two cables 37 wrappingclockwise thereabo-ut, and the outer ends of the cables 31 pass aroundsheaves 37a at the outer end of the boom H, and, running in oppositdirections from the sheaves 31a, pass about the sheaves 31b and thenceback along the boom at its opposite sides to points of connection withthe opposite sides of the inner bucket supporting means at 370, as moreparticularly described later.

The cables 40 located with their bights in a vertical plane and disposedat the outer sides of the boom H are endless cables connected with therespective drums ll, l8 for moving the outer bucket 2| inwardly andoutwardly under power. Said cables are attached to the outer bucket, andoperation of the clutch means [5a and 28a, as previously described,under manual control will elfect reverse movements of the cables 42 forthe purpose mentioned. Suitable sheaves or pulleys 40a at the outer endof the boom H and opposite sides thereof guide the cables 40 at thesepoints, and fleeting sheaves 5| engage the upper laps of the cables nearthe drum shaft i6, and other fleeting sheaves 52 engage the lower lapsof the cables 40 near the location of the sheaves 5!.

The boom H comprises side structural members preferably channels or thelike and said boom includes two main parts, an inner stationary tracksection 24 and an outer pivoted and variably inclinable track section25. The relatively stationary section 24 is made up of two curved sidemembers having supporting means including suitable bracket F forsupporting the shaft l6. The bracket means F provides a bearing for thevertical shaft 8 at the lower end of the latter so that said shaft formsa vertical axis about which the boom H as a complete unit may be swunghorizontally.

'The boom H may be tilted sidewise to compen sate for any elevation inthe roa'dbed on curves.

The inclinable or pivotal section 25 of the boom H is hinged to thesection 24 at opposite sides of the boom sections as at the points I andthus may be raised or lowered by suitable mechanism very similar to thatheretofore employed for raising and lowering single boom typedistributing units, said mechanism to be more fully describedhereinafter.

Carried by the boom H at one side thereof, see Figures 1, 6 and 8, in anangle plate 2'! supported by arms 28 on a shaft 26, in turn mounted insuitable bearings in crosspieces or members connecting the structuralside members of the boom H. The angle plate 21 is of considerable lengthextending from the inner end of the inclinable section 25 of the boom toa point a short distance from the outer end of said section,

On the inner end of the shaft 25 is a lever arm 29 connected by a link30 to a clutch throw out lever B! which operates the clutch means 230.inside the cable drum 23. The parts just last described comprise aclutch knock-out mechanism designed to discontinue the outward movementof the inner bucket 22 when said bucket reaches its outer limit ofmovement at the inner side of the outer bucket and its discharge door22a is opened to discharge the contents of the bucket 22.

Describing the clutch knock-out mechanism last referred to somewhat morefully, assuming that the outer bucket 21 has been caused to traverse theboom H to a suitable point of discharge in the length of the boom, saidbucket 2| will be stationary. Then, when the bucket 22 is caused to passoutwardly on the boom, when it reaches the bucket 21, the over deadcenter crank arm 32 connected by the rod 32a to the door 22a will beopened by striking the inner end 33 of a link 46 which is mounted on thefront bucket 2!. In this manner the upper end of the arm 32 is carriedover the dead center and swings leftwardly downwardly as the door 22aopens. In this swinging movement the arm 32 hits a lever 34 on thebucket 22 and thereby raises a vertically movable actuating bar 35sliding on the roller bracket of the bucket 22. The raising movement ofthe actuating bar 35 causes it to strike the plate or angle 21 rockingthe angle upwardly and thereby rocking the shaft 23 thus to actuate theparts 29, 30, and 3| to throw out the clutch means 23a and bring thebucket 22 to a stop. The parts 34 and 35 are mounted on the rollercarrier or bracket 36 of the bucket 22.

Since the bucket 22 moves by power in the outward or forward directiononly, a means has to be provided to keep the cables 31 taut at all timesand such means comprise a drag brake 38 inside the drum 23 that isconnected with the cable 31.

Figure 1 and Figure 10 show how the cables 40 Which are anchored in thedrums H and i3 are connected by links 42 to pivots in the upper end oflevers 43, in turn pivoted at 43a to the roller carriers or brackets 44of the bucket 2 I. A pivoted arm 45 on the roller carrier 44 is alsopivotally connected at its upper end by link 43 with the lever 43.

Upon engagement of the clutch means I Eat, the cables 40 are operated topull outwardly on the links 42, and the levers 43 at opposite sides ofthe bucket and roller carrier 44 engage a protrusion or abutment on thecarrier 44 and cause the bucket 2! to be pulled outwardl by the movementof said cables. As is a similar practice in present types of boom andbucket paving machines, upon reversal of movement of the cables 49 byuse of the clutch means 26a, the cables 40 will cause the links 45 tocontact with the over dead center crank arm 4? connected by the linkage56 to the door Zia of the bucket 2i. This striking action of the member45 against the arm 41 throws the latter over its dead center positionand enables the door 2! a to open and discharge the bucket 25,

For closing of the buckets on their simultaneous empty return trip tothe drum of the mixer, there are provided toothed segments 48 on theaxes 48a of the dead center arms 4? and 32 of the respective outer andinner buckets 2i and 22. v These toothed segments are of courseuprai'sed by the throw-over action of the dead center arm in opening thedoors Ma and 220.. Therefore when the two empty buckets 2i and 22 returnto the inner end of the boom H after depositing their contents on thesubgrade, the toothed segments 48 of the inner and outer buckets inconsecutive order will engage a toothed rack member 49 on the innersection 24 of the boom H and by such engagement a clockwise rotarymotion of the segments will be created, thus carryin the arms 4? and 32in a clockwise return direction to raise the doors of the buckets andlock them by the arms being shifted to their rightward over dead centerposition respecting the axes 48a.

With he. me hanism of he nv ti n s u far. described in reference to allmain and essena e tu es h f, t e e ral e at n o he tandem bucketdistributing boom unit will beset forth.

By control of the clutch means la, the, lowerlaps of the cables 40 arecaused to pull o twardly, on the links 42 to carry the filled outerbucket}! outwardly on the boom H to the placewhere it is, to be emptiedfor deposit of its contents The clutch means Elia is then operated toreversethe movement of the cable means 4;] andthis will dump the bucket21 in the manner previously described by action of the bottom door ofsaid bucket. Half the mixed charge of the drum Ais h e osit n e. ubt a tNext, by operation of the clutch means 23;: manually, the operator willcause the inner bucket 22, previously filled with concrete aggregates,to move outwardly on the boom H until its bucket door holdin and closingarm 32 strikes the member 33 of the bucket 21, thereby tilting the arm32 and permitting the door 22a of bucke 22to open and discharge thebucket. Ofcourse, when the bucket door 22a opened, the arm 32 struck thelever 34, raised the actuating bar 35, and operated the clutch means 29ato release these clutch means and stop the outward movement of thebucket 22, simultaneously with its discharge and previously to anyimpacting action of the bucket 22 against the bucket 2|.

The clutch means a may again be thrown in, this time to remain clutchedfor bringing the outer bucket back to its position for loading at t emixing drum. In this action the cables Gil exert an inward pushing forceon the links 32 connected with the bucket 21 and the bucket 2 exerts apushing force against the outer side of the bucket 22 so that bothbuckets move back to the mixing drum simultaneously. Upon reaching'theproper position adjacent the mixing drum, the operator will release theclutch means Zllaand permit stopping movement of-the buckets in theirinward traverse on the boom H.

The boom H, being made of two sections, it is possible to elevate theouter section by movement about its pivotal axes I through means of boomraisin cable instrumentalities 55 which are anchored. to thesuperstructure frame B as t 56, the cable means passing around a sheaveon the outer end of the boom, sheaves at the anchoring means 56, a guidesheave 51, a second uide sheave 53, to a winding drum 59.

Irrespective of the inclination of the boom section 25 relatively to theboom section 24, they buckets 2i and 2.2 may be caused to travel alongthe boom from the inner to-the outer end thereof.

Respecting certain details of construction that may be employed, it isapparent from Figure 1 of the drawings that from the gearing of thehousing 5a vertical shaft 6i} carries the drive to the drum 59 and thelower end of said shaft Ellis connected by bevel gears 6| to ahorizontal shaft 62 which supports a, worm gear 53 engaging anarc-shaped rack 64 on a bracket 65 at the inner end of the boom H. Theoperation of the shaft 55 under manual control may be used, therefore,to swing the boom H horizontally and this operation is known in the art;The boom swings about the shaft 8 as an axis, as indicated previously.

When the outer boom member or section 25 isv raised from the positionofFigure 1 in full lines, toan upward position as illustrated brokenlyin dotted lines in said figure, the sheaves 5 I mounted on the boomsection 24 contact with the cables fll),

and take up they resultant slack therein due to decreasing the centerdistance between the sheaves M and the cable drums H and 18. An idlerroller 52 near, the outer end of the boom section 24 prevents. the cableparts 31 from contacting with the cross members of the boom. The rollers66 on the roller carriers 35 and 44 travel, of course, in the channelportions of the side structural members of the boom sections 24 and 25.They pass over the hinge member I as they move. from the section 24 tothe section 25 of the boo-m.

As previously indicated, any suitable manual instrumentalities may beutilized for controlling the several clutch means [5a, 23a and 20a. Asil-' lustrated, said clutches are controlled from a lever 5! swingablein a plane longitudinal of and parallel to the boom and shiftablerectilinearly to such plane about a pivot 58. The lever 51 is engageableby outward lateral movement with a throw arm and by inward lateralmovement with a throw arm ill. The arm 59 is mounted on an inner solidshaft H and the arm is mounted on a hollow shaft 12 in which the shaft His received. The positions of the lever 61 are indicated upon a slottedplate it through which the lever handle passes and by propermanipulation of the lever from a neutral position outwardly andrearwardly, it may be engaged with the arm 69 to effect an outhaul ormovement of the inner. bucket 22. Shifting the lever 6'! across neutralin an opposite direction, and rearwardly, will cause the proper clutchmeans to move the outer bucket 52% outwardly on the boom and an oppositeor rearward movement of the lever 6'! when so adjusted will cause theinward movement of the bucket 2! on the boom, which movement of coursesimultaneously brings the bucket 22 back to charging position near themixer by pushingace tion previously described.

Figure l discloses that the shafts H and 12 are mounted on the bracket Fand are equipped with suitable yokes l5 engaging the throw sleeves15 onthe shaft 8, one sleeve 15 connected by a lever 16 to suitable linkageleading to the operating clutch for causing outward movement of theinner bucket and a second lever l1 being connected by suitable linkageand lever parts to the clutches that control the outward pull ortraverse of the bucket 2i along the boom, and the return traversethereof.

As apparent from the drawings, Figures 2, and 11 to 13 inclusive, themain supporting arm or bracket} at its lower portion 'i'S'is adapted tobe received in the socket portion 19 at the left upper part of the swingbracket 55, see Figure 12. This affords a vertical axis for thehorizontal swinging of the boom unit H. In turn the boom unit Hisequipped on the inner section 24 thereof with a special bracket 85adapted at its portions.

Mia and b to be connected by horizontal pivot pins or pintles with theportions 79a and 19b, respectively, of the bracket 55. This constructionaffords a longitudinal horizontal axis connecti-on between the boom unitH and bracket 65.

Such construction is advantageous in that even if the traction base C ofthe machine is not horizontal transversely, the boom and buckets unitwill be properly positioned in virtual suspension may swing.transversely to such axisabout the,

pivotal axis established by the parts 88a and 80b,

and 19a and 19b, and the outer section 25 of the boom unit I-I may swingvertically about the axis I connecting the sections 24 and 25.

Having thus described my invention, what I claim as new and desire tosecure by Letters Patent of the United States, is:

1. In a concrete distributing machine of the class described, incombination, a materials discharge device, a boom and bucket unitextending from the discharge device, tandem buckets movable in the sameline of movement on the boom of said unit, operating mechanism forcausing independent travel movement of the buckets in alinementoutwardly on said boom, and a distributor intermediate the dischargedevice and the said buckets for dividing the aggregates discharged fromthe discharge device to cause passage of the same to both of thebuckets.

2. A machine as claimed in claim 1, combined with a driven shaftconstituting a vertical pivotal axis for the boom and bucket unit, andan operating connection between said shaft and the distributor,

3. A machine as claimed in claim 1, combined with a driven shaftconstituting a vertical pivotal axis for the boom and bucket unit, andan operating connection between said shaft and the distributor, theoperating mechanism for the buckets including instrumentalitiesconnected with said shaft.

4. A boom and bucket unit for concrete paving machines, comprising asupport, a boom extending from the support and movably mounted upon thelatter, tandem inner and outer buckets arranged to travel from a normalloading position in which they are carried by the boom to an outwarddischargin position and thence to return to their loading position,discharging means for each bucket, said buckets disposed in inward andoutward alinement with each other to travel in the same line of movementon the boom, and means to move said buckets inwardly and outwardly onthe boom.

5. A boom and bucket unit for concrete paving machines, comprising asupport, a boom extending from the support and movably mounted upon thelatter, tandem inner and outer buckets arranged to travel from a normalloading position in which they are carried by the boom to an outwarddischarging position and thence to return to their loading position,discharging means for each bucket, said buckets disposed in inward andoutward alinement with each other to travel in the same line of movementon the boom, and means to move said buckets inwardly and outwardly onthe boom, separately in an outward direction, and to cause engagement ofthe outer bucket with the inner bucket to effect inward movement of thelatter.

6. A boom and bucket unit for concrete paving machines, comprising a,support, a boom extending from the support and movably mounted upon thelatter, tandem inner and outer buckets arranged to travel from a normalloading position in which they are carried by the boom to an outwarddischarging position and thence to return to their loading position,discharging means for each bucket, said buckets disposed in inward andoutward alinement with each other to travel in the same line of movementon the boom, means to move said buckets inwardly and outwardly on theboom, and means on the outer bucket to trip the discharge means for theinner bucket.

7. A boom and bucket unit for concrete paving machines, comprising asupport, a boom extending from the support and movably mounted upon thelatter, tandem inner and outer buckets arranged to travel from a normalloading position in which they are carried by the boom to an outwarddischarging position and thence to return to their loading position,discharging means for each bucket, said buckets disposed in inward andoutward alinement with each other to travel in the same line of movementon the boom, and means to move said buckets inwardly and outwardly onthe boom operable to effect independent outward movement of the bucketson the boom and compel simultaneous inward movement of said buckets.

8. A boom and bucket unit for concrete paving machines, comprising asupport, a boom extending from the support and movably mounted upon thelatter, tandem inner and outer buckets arranged to travel from a normalloading position in which they are carried by the boom to an outwarddischarging position and thence to return to their loading position,discharging means for each bucket, operating means for causingindependent movement of the buckets on the boom from the loadingposition to the discharging position, and including means for effectingsimultaneous movement of the buckets to return them to their loadingposition, combined with operating means for the discharging means of theouter bucket, and instrumentalities intermediate the outer bucket andinner bucket for operating the means of discharging the latter bucket,comprising parts on both buckets contacting one another as the innerbucket reaches a discharging position substantially engaging orcontacting the outer bucket.

9. In a boom and bucket distributing unit for concrete mixing machines,in combination, a support, a boom mounted on said support for movementrelative thereto, tandem buckets mounted on the boom to traverse thesame longitudinally from an inner loading position to an outerdischarging position, operating mechanism for effecting movement of onefirst bucket outwardly on the boom and controlling discharge action ofsaid bucket, operating means for the second bucket for moving same fromits loading position to a discharging position on the boom independentlyof the movement of the first bucket, and means for automaticallydischarging the second bucket when it reaches a position adjacent to thedischarge position of the first mentioned bucket, the last meansincluding instrumentalities on the first mentioned bucket for impingingand operating the discharge mechanism of the second mentioned bucket toefiect discharging action of the latter.

10. In a boom and bucket distributing unit for concrete mixing machines,in combination, a support, a boom mounted on said support for movementrelative thereto, tandem buckets mounted on the boom to traverse thesame longitudinally from an inner loading position to an outerdischarging position, operating mechanism for effecting movement of onefirst bucket outwardly on the boom and controlling discharge action ofsaid bucket, operating means for the second bucket for moving same fromits loading posi- 7 tion to a discharging position on the boom inde- T15bucket, comprising control means on the second a Number 11 mentionedbucket engageable with-means on the first bucket at the dischargeposition of the latter to dischargethe second bucket, and in which theoperating mechanism for the buckets is operable to simultaneously returnthe buckets to their loading'positions. I

RAYMOND A. BECKWITH.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date 542,375 Scoles July 9, 1895 Number

